Kumanu Tāngata—The Aftermatch Project: Neurodegenerative Disease Epidemiology in Former First-Class New Zealand Rugby Players

Abstract

Background: Growing concern surrounds the risk of neurodegenerative diseases in high-level collision sports. Despite participant exposure to repetitive head acceleration events and concussions, research on rugby union's connection to these diseases is limited.

Methods: This retrospective cohort study in New Zealand compared males who played high-level rugby between 1950 and 2000 (n=12,861) with males from the general population (n=2,385,543), matched by age, ethnicity, and birthplace. We used Cox proportional hazards models to assess risks of Alzheimer's disease, Parkinson's disease, motor neuron disease, and other dementias.

Findings: A higher percentage of rugby players (4·7%) than the general population (3·9%) developed neurodegenerative diseases. Hazard ratios indicated increased risks for any neurodegenerative disease (1·17 [95% CI 1·08–1·27]), Alzheimer's disease (1·42 [95% CI 1·22–1·66]), and other dementias (1·16 [95% CI 1·05–1·27]). Risks for Parkinson's disease (HR 1·09 [95% CI 0·92–1·29]) and motor neuron disease (HR 1·02 [95% CI 0·70–1·51]) were similar between the groups. Greater rugby exposure correlated with somewhat higher risk e.g., HR 1·39 [95% CI 1·22–1·59] for any neurodegenerative disease for six or more years of play. Players in forward positions had lower disease incidence than backline players (HR 0·81 [95% CI 0·67–0·98]). Differences between international/professional and provincial/amateur players were minimal (HR 0·78 [95% CI 0·54–1·15]).

Interpretation: High-level rugby in New Zealand is associated with a slight to moderate increase in neurodegenerative disease compared to the general population.

Funding: The project was funded by World Rugby and the New Zealand Rugby Foundation.

Declaration of Interest: KQ has been employed by New Zealand Rugby since 2000 and currently occupies the role of Chief Scientist, New Zealand Rugby. He also sits on World Rugby’s Scientific Committee and has contributed to various World Rugby working groups focussed on player welfare issues from 2011 to the time of publication. KQ’s input into the project was conducted in collaboration with his co-authors, who are independent of New Zealand Rugby and World Rugby, and he declares that at no time did NZ Rugby, nor the funding agencies World Rugby and the New Zealand Rugby Foundation provide advice or input into the data analysis, interpretation of the findings, or the manuscript preparation. A copy of the submitted draft of the project was provided to the funding bodies and New Zealand Rugby at the time of submission. AJG has been a contracted concussion consultant to Rugby Australia since July 2016. He is a member of the World Rugby Concussion Working Group. He has received travel funding or been reimbursed by professional sporting bodies, and commercial organisations for discussing or presenting sport-related concussion research at meetings, scientific conferences, workshops, and symposiums. He has a clinical practice in neuropsychology involving individuals who have sustained sport-related concussion (including current and former athletes). He is a member of the Australian Football League Concussion Scientific Advisory Committee. He is supported by a National Health and Medical Research Council (NHMRC) Investigator Grant. He acknowledges unrestricted philanthropic support from the National Rugby League for research in former elite-level rugby league players. IM was employed by New Zealand Rugby from 2012 – 2019 as the Chief Medical Officer. During this time, he also held various committee appointments with World Rugby focused on player welfare matters. All other authors declare no conflicts of interest.

Ethical Approval: Ethics approval was granted by the Auckland Health Research Ethics Committee (Ref. AH23203). This study followed the Strengthening the Reporting of Observational studies in Epidemiology (STROBE) guideline

Keywords: Neurodegenerative diseases, Rugby union, administrative data, collision sports, athlete health, retrospective cohort study